Drive sprocket for a tracked vehicle

Abstract

A snowmobile is propelled by an endless track that is operatively connected to the snowmobile's engine by two drive sprockets. Each drive sprocket includes one set of external teeth and two sets of internal teeth that engage three corresponding sets of track teeth formed on the track. Alignment cleats are mounted on the inside of each of one of the sets of track teeth. During low-load operation, contact between the cleats (and the track teeth on which the cleats are mounted) is minimized or eliminated, which reduces or eliminates noise caused by collisions between the metal sprocket and the metal cleats. During higher load operation, the track deforms such that the set of external sprocket teeth engage the cleats and associated set of track teeth.

1. A sprocket for a vehicle having an endless track and a power plant, the sprocket comprising:
 a sprocket wheel operatively interconnected with the power plant of the vehicle, the sprocket wheel having a rotational axis, a perimetrical surface, and first and second axial surfaces; 
 a first plurality of teeth extending radially outwardly from the perimetrical surface in spaced-apart relation; 
 a second plurality of teeth extending axially outwardly from the first axial surface in spaced-apart relation; and 
 a third plurality of teeth extending axially outwardly from the second axial surface in spaced-apart relation, 
 wherein, in a circumferential direction, each of the second plurality of teeth are wider than each of the first plurality of teeth. 
 
   
   
     2. The sprocket according to  claim 1 , wherein each of the second plurality of teeth define an outward surface disposed radially farther from the rotational axis than the perimetrical surface. 
   
   
     3. The sprocket according to  claim 1 , wherein each of the second plurality of teeth defines two notches therein. 
   
   
     4. The sprocket according to  claim 3 , wherein each of the second plurality of teeth has a base portion and a tip portion, and the notches are formed in the base portion. 
   
   
     5. The sprocket according to  claim 1 , wherein each of the second plurality of teeth has base portion and a tip portion, where the tip portion has a notch formed therein. 
   
   
     6. The sprocket according to  claim 5 , wherein each of the third plurality of teeth has base portion and a tip portion, where the tip portion has a notch formed therein. 
   
   
     7. The sprocket according to  claim 1 , wherein each of the first plurality of teeth is formed on a corresponding outer surface of one of the second plurality of teeth. 
   
   
     8. The sprocket according to  claim 1 , wherein, in a circumferential direction, each of the third plurality of teeth are wider than each of the first plurality of teeth. 
   
   
     9. The sprocket according to  claim 8 , wherein each of the first plurality of teeth is formed on a corresponding outer surface of at least a portion of one of the second plurality of teeth and the third plurality of teeth. 
   
   
     10. A sprocket for a vehicle having an endless track and a power plant, the sprocket comprising:
 a sprocket wheel operatively interconnected with the power plant of the vehicle, the sprocket wheel having a rotational axis, a perimetrical surface, and first and second axial surfaces; 
 a first plurality of teeth extending radially outwardly from the perimetrical surface in spaced-apart relation; and 
 a second plurality of teeth extending axially outwardly from the first axial surface in spaced-apart relation, 
 wherein, in a circumferential direction, each of the second plurality of teeth are wider than each of the first plurality of teeth. 
 
   
   
     11. The sprocket according to  claim 10 , wherein each of the second plurality of teeth has at least one notch formed therein. 
   
   
     12. The sprocket according to  claim 11 , wherein each of the second plurality of teeth has a base portion and a tip portion, wherein a pair of notches are formed on opposing sides of the base portion. 
   
   
     13. The sprocket according to  claim 11 , wherein each of the second plurality of teeth has a base portion and a tip portion, wherein a notch is formed on the tip portion. 
   
   
     14. The sprocket according to  claim 10 , wherein, each tooth of the first plurality of teeth is formed on an outer surface of a corresponding tooth of the second plurality of teeth. 
   
   
     15. A vehicle comprising:
 a frame; 
 a power plant supported by the frame; 
 a sprocket operatively connected to the power plant, the sprocket comprising:
 a sprocket wheel rotationally supported by the frame and operatively connected to the power plant, the sprocket wheel having a rotational axis, a perimetrical surface, and first and second axial surfaces, 
 a first plurality of sprocket teeth extending radially outwardly from the perimetrical surface in spaced-apart relation, 
 a second plurality of sprocket teeth extending axially outwardly from the first axial surface in spaced-apart relation, and 
 wherein, in a circumferential direction, each of the second plurality of teeth are wider than each of the first plurality of teeth; and 
 
 an endless track supported by the frame, the endless track passing around and engaging the sprocket. 
 
   
   
     16. The vehicle according to  claim 15 , wherein the endless track comprises:
 a belt having an outer side and an inner side, the belt defining a plurality of holes therethrough, the portions of the belt therebetween being a first plurality of track teeth; 
 a plurality of lugs projecting from the outer side: and 
 a second plurality of track teeth projecting from the inner side, the second plurality of track teeth engaging the second plurality of sprocket teeth. 
 
   
   
     17. The vehicle according to  claim 16 , wherein each of the first plurality of track teeth longitudinally registers with each of the second plurality of track teeth, and each of the first plurality of sprocket teeth are axially aligned with each of the second plurality of sprocket teeth. 
   
   
     18. The vehicle according to  claim 16 , wherein the sprocket further comprises a third plurality of sprocket teeth extending axially outwardly from the second axial surface in spaced-apart relation, and the endless track further comprises a third plurality of track teeth projecting from the inner side, the third plurality of track teeth engaging the third plurality of sprocket teeth. 
   
   
     19. The vehicle according to  claim 18 , wherein each of the second and third pluralities of track teeth are disposed laterally adjacent to each of the first plurality of teem, on opposite sides thereof. 
   
   
     20. The vehicle according to  claim 19 , wherein each of the first plurality of sprocket teeth, each of the second plurality of sprocket teeth, and each of third plurality of sprocket teeth are axially aligned. 
   
   
     21. The vehicle according to  claim 16 , wherein, when the endless track does not deform, the first plurality of track teeth do not engage the perimetrical surface. 
   
   
     22. The vehicle according to  claim 21 , wherein, when the endless track does not deform, the first plurality of track teeth do not engage the first plurality of sprocket teeth. 
   
   
     23. The vehicle according to  claim 21 , wherein the second plurality of track teeth comprise a flexible, resilient material, and
 wherein, when the second plurality of track teeth deform under a load exerted thereon by the second plurality of sprocket teeth, the first plurality of sprocket teeth engage the first plurality of track teeth to supplement traction between the sprocket and the endless track. 
 
   
   
     24. The vehicle according to  claim 23 , wherein:
 the endless track further comprises a plurality of cleats, each cleat including a base portion secured to one of the first plurality of track teeth and at least one cleat portion projecting from the base portion away from the inner side, 
 when the second plurality of track teeth do not deform, the base portions of the cleats do not contact the perimetrical surface; and 
 when the second plurality of track teeth deform under a load exerted thereon by the second plurality of sprocket teeth, the first plurality of sprocket teeth engage the cleats to enhance traction between the sprocket and the endless track. 
 
   
   
     25. The vehicle according to  claim 16 , wherein the perimetrical surface defines a sprocket valley between adjacent teeth of the first plurality of sprocket teeth, the inner side of the belt defines a track valley between adjacent teeth of the second plurality of track teeth, each of the second plurality of sprocket teeth defines an outward surface, and the outward surfaces of the second plurality of sprocket teeth engage the track valleys as the sprocket rotates such that when the endless track does not deform, the first plurality of track teeth do not contact the sprocket valleys. 
   
   
     26. The vehicle according to  claim 25 , wherein the outward surfaces of the second plurality of sprocket teeth are disposed radially further from the rotational axis than the sprocket valleys. 
   
   
     27. The vehicle according to  claim 25 , wherein the endless track further comprises a plurality of alignment cleats, each cleat including a base portion secured to one of the first plurality of track teeth and at least one cleat portion projecting from the base portion away from the inner side, and
 wherein, when the endless track does not deform, the base portions of the cleats do not contact the sprocket valleys. 
 
   
   
     28. The vehicle according to  claim 16 , wherein the endless track comprises a resilient, flexible material, and wherein the first and second pluralities of track and sprocket teeth are sized and spaced such that the first plurality of sprocket teeth drivingly engage the first plurality of track teeth only when a portion of the endless track deforms longitudinally as the second plurality of sprocket teeth apply pressure to the second plurality of track teeth. 
   
   
     29. The vehicle according to  claim 16 , wherein the endless track further comprises a plurality of cleats, each cleat including a base portion secured to one of the first plurality of track teeth and a cleat portion projecting from the base portion away from the inner side, and
 wherein, when the endless track is laterally aligned with the sprocket, the cleat portions do not touch the sprocket as the sprocket rotates. 
 
   
   
     30. The vehicle according to  claim 16 , wherein:
 the endless track further comprises a plurality of cleats, each cleat including a base portion secured to one of the first plurality of track teeth and a cleat portion projecting from the base portion away from the inner side, 
 each of the second plurality of sprocket teeth defines two notches, and 
 as the sprocket rotates, the cleat portions extend into the notches of adjacent ones of the second plurality of sprocket teeth. 
 
   
   
     31. The vehicle according to  claim 30 , wherein each of the second plurality of sprocket teeth has a base portion and a tip portion, and the notches are formed in the base portion of the second plurality of sprocket teeth. 
   
   
     32. The vehicle according to  claim 16 , wherein the first plurality of track teeth engage the first plurality of sprocket teeth as the sprocket rotates. 
   
   
     33. The vehicle according to  claim 18 , wherein each of at least one of the second plurality of teeth and the third plurality of teeth has at least one notch formed therein. 
   
   
     34. The vehicle according to  claim 33 , wherein each of the second plurality of teeth and the third plurality of teeth has a base portion and a tip portion, wherein a pair of notches are formed on opposing sides of the base portion. 
   
   
     35. The vehicle according to  claim 33 , wherein each of the second plurality of teeth and the third plurality of teeth has a base portion and a tip portion, wherein a notch is formed on the tip portion of at least one of the second plurality of teeth and the third plurality of teeth. 
   
   
     36. The vehicle according to  claim 15 , wherein, in a circumferential direction, each of the second plurality of teeth and the third plurality of teeth are wider than each of the first plurality of teeth.